In automotive technology, “brake-by-wire” brake systems are becoming increasingly common. Such brake systems often comprise, as well as a brake master cylinder which can be actuated by the vehicle driver, an electrically controllable pressurization device by means of which the wheel brake can be actuated in “brake-by-wire” operating mode.
International patent application WO 2011/029812 A1 discloses a “brake-by-wire” brake system with a brake pedal-actuated brake master cylinder, a travel simulator and a pressurization device. The wheel brakes are pressurized by the pressurization device in the “brake-by-wire” operating mode. In fall-back operating mode, the wheel brakes are pressurized by means of the brake master cylinder which is actuatable by the brake pedal.
DE 10 2011 081 461 A1 discloses a brake system for motor vehicles which comprises a brake pedal-actuatable brake master cylinder which is separably connected to the wheel brakes of the motor vehicle, an electrically controllable pressurization device which can be connected to the wheel brakes, a pressure regulating valve arrangement and an electrically controllable additional pressurization device. The primary piston of the brake master cylinder can be actuated by means of the additional pressurization device. For this the pressure output port of the additional pressurization device is connected to an intermediate space of the brake master cylinder which is delimited by the brake pedal-side surface of the primary piston of the brake master cylinder. The additional pressurization device is thus connected upstream of the brake master cylinder and creates a brake force amplification of an actuating force introduced by the driver via the brake pedal. It is not possible to feed (a volume of) pressure medium into the brake circuits or wheel brake circuits from the additional pressurization device.
It is an object of the present invention to propose a brake system with which the safety requirements of autonomous driving are fulfilled. Braking must be possible in the event of a fault even without actuation of the brake pedal by the driver.
This object is achieved by a brake system according to this invention.